This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to 9903909-1 filed in Sweden on Oct. 29, 1999; the entire content of which is hereby incorporated by reference.
The present invention relates to antennas integrated into a RF module and more particularly to antenna integration for RF modules utilizing a shielding member.
The utilization of RF modules for transferring data and other signals is an increasing branch in modern techniques. There is a general aim of using wireless communication to terminals and auxiliary equipment to avoid having a lot of cables interconnecting the devices. A typical frequency for this may for instance be a range of the order 1 to 5 GHz. One problem within the techniques of using small RF modules is to obtain an effectively operating antenna within the very limited space offered by the small RF module itself. Prior art discloses mostly the use of an external antenna, which means that RF signals are fed from the RF module to the main printed circuit board (PCB) and therefrom to the external antenna, which may be on the PCB or mounted at another location.
One approach for solving some of the problems with an external antenna has been the utilization of ceramic antennas, but with the drawback of increased weight and difficulties in tuning the antenna during production/soldering, besides printed circuit board mounted external antennas require space on the PCB.
There are found numerous documents discussing antenna solutions within a limited space. A representative technical field for this is for instance in connection to radio pagers. For example a document U.S. Pat. No. 5,678,216 discloses a radio pager with a half-size micro-strip antenna. A pair of electrically conductive elements is surrounding a PCB onto which the pager circuitry components are mounted. The conductive elements form an electromagnetic shield case for the circuitry elements. The micro-strip antenna is then carried by one of the conductive elements.
Another document EP-A1-0 707 335 discloses an antenna device designed to increase the volume, which it occupies in a mobile communication apparatus as well as to achieve a large gain and a wide frequency band width without occupying a large area on a main printed circuit board and without changing the size of the apparatus.
A Japanese document JP6260949 discloses a solution for protecting the electronic equipment from static electricity and also preventing undesired radiation in a limited space without deteriorating the antenna gain by using an antenna which doubles as a shielding case. A multi-layer printed board includes four layers where a second layer is used as a circuit blocking ground and a third layer forming an antenna portion connected in series with a U-shaped antenna portion doubling as a shielding case. The first and fourth layers are carrying the components of the electronic circuitry.
However documents according to the state of the art disclosed so far does not present an optimum desired solution for an antenna module suitable for a RF module including a small RF sub-module. There is still a demand for a solution enabling easy antenna integration and optimum tuning of the antenna operational frequency in connection to the production/soldering of a small RF module.
The present invention discloses integration of a RF antenna into a RF shielding part of a RF module and presents simultaneously a unique tuning mechanism for tuning the RF antenna according to a Voltage Standing Wave Ratio (VSWR) specification to thereby tolerate bigger tolerances of the other components on the printed circuit board. Thereby more space at the PCB is also obtained as well as avoiding RF losses in transmission lines and soldering connections to an external antenna. The risks of stop in the production process due to that an integrated antenna being out of VSWR specification then also will be eliminated.
A module antenna device according to the present invention is set forth by the independent claim 1 and further embodiments are set forth by the dependent claims 2 to 10.